Die: loss of individuals, populations (extirpation), or species (extinction)
Is extinction actually a response?
The die ‘response’ is more a a failure to move, adjust or adapt
But patterns of extinction are so important that we need to treat it as a core category
Modern day biodiversity reflects billions of years of speciation
Modern day biodiversity reflects billions of years of speciation
Balanced by billions of years of extinction
What is different about today?
2011, cited 3964 times
Never before has an extinction spasm been caused by a single species at such high velocity
“The analysis we present here avoids using assumptions … which can suggest very high extinction rates, and which have raised the possibility that scientists are “alarmists” seeking to exaggerate the impact of humans on the biosphere”.
Cumulative percentage of extinct species for vertebrates. Dashed line is number of extinctions expected under a background extinction rate of 2 E/MSY
Number of years it would take for the vertebrate extinctions since 1900 to occur under the background extinction rate of 2 E/MSY
Current amphibian extinction rates are 100 times higher than historical background rates
Current amphibian extinction rates are 100 times higher than historical background rates
Emerging infectious disease
Where did the chytrid fungus come from?
How has it spread?
How does it kill frogs?
Are all chytrid strains equally deadly?
Why are some frog species more susceptible than others?
What can we do to protect amphibian biodiversity?
And on…
Emerging infectious disease
Where did the chytrid fungus come from?
How has it spread?
How does it kill frogs?
Are all chytrid strains equally deadly?
Why are some frog species more susceptible than others?
What can we do to protect amphibian biodiversity?
And on…
How does Bd kills frogs
Amphibians are infected with Bd by contact with other animals or by spores floating in the water
Eats away at their skin and triggering fatal heart attacks
Before it dies, a frog may manage to hop its way to a new stream or pond, spreading the fungus further.
Where did Bd come from?
How much genetic diversity does it contain?
Museum specimens point to the oldest known instance from South Africa in the 1930’s.
?Spread around the world in African clawed frogs used for human pregnancy tests?
Genetic evidence of virulence: some of these gene families serve as virulence factors in other fungi that infect vertebrate skin
Why do some frogs NOT die from Bd infection?
Resistant frogs mount a more robust immune response (via plasticity)
500 species of amphibians have declined significantly because of the outbreak — including at least 90 species presumed to have gone extinct (2019)
Tracking population recoveries
Direct support to mangers working on-the-ground for amphibian conservation
Pinnacles biologists conducted a study of Bd at Pinnacles National Park from 2006-2007
Tested animals for Bd by swabbing their skin and sending the swabs to a lab for DNA analysis
All three frog and toad species we tested at Pinnacles are infected with Bd
Rarely find dead frogs, and frog populations appear to remain stable
Contributions to conservation more broadly
Intentional extinction of pathogens & parasites?
British biotech firm this week got the green light from U.S. regulators to release over 2 million genetically modified mosquitoes in Florida and California
Effort to combat transmission of diseases like Zika, dengue fever and canine heartworm
Genetically modified male (non-biting) mosquitoes mate with invasive female Aedes aegypti mosquitoes, mediating a reduction of the target population as the female offspring of these encounters cannot survive